Gyroscopic platform assembly



June 30, 1970 c. H. WILL; JR 3,517,563

GYROSCOPIC PLATFORM ASSEMBLY Filed March 2, 1966 4 Sheets-Sheet 1 FIG. j

a) a) a) INVENTOR.

CHRISTIAN H. WILL, JR.

' ATTORNEYS June 30, 1970 c. H. WILL, JR

GYROSCOPIC PLATFORM ASSEMBLY 4 Sheets-Sheet 3 Filed March 1966'JNVENTOR. CHRISTIAN H. WILL.JR.,

ATTORNEYS.

June 30, 1970 C. H. WILL, JR

GYROSCOPIC PLATFORM ASSEMBLY 4 sheets sheet 5 Filed March 2, 1966 6lb64b FIG.54

' ATTORNEYS June 30, 1970 c. HQWILL, JR

GYRO SCOPIC PLATFORM ASSEMBLY Filed March 2, 1966 4 Shets-Sheet 4.

. mm mm 00 INVENTORY v CHRISTIAN H. WILL, JR.

y v ATTORNEYS United States Patent 3,517,563 GYROSCOPIC PLATFORMASSEMBLY Christian H. Will, Jr., Grand Rapids, Mich., assignor to LearSiegler, Inc. Filed Mar. 2, 1966, Ser. No. 541,874 Int. Cl. G01: 19/02US. Cl. 745.34 11 Claims ABSTRACT OF THE DISCLOSURE This inventionrelates to gyroscopic platform assembhes utilizing an inside-outgimballing arrangement wherein the component mounting platforms areindividually and independently rotatably affixed to a pair of axiallyaligned supports. The relative rotational positions of the platforms aremaintained by aflixing a circular rack gear to the inner face of each ofthe platforms. A pair of spur gears each having a diameter substantiallyless than that of the rack gears are carried by the succeeding outergimbal frame so as to transmit the rotational thrust of one of theplatforms directly to the other platform.

This invention relates to gyroscopic platform assemblies and, moreparticularly, to such assemblies utilizing an inside-out gimballingarrangement.

There are two major modes of gimballing which may be utilized in thedesign and fabrication of stabilized platforms. These are traditionallydenoted as the outside-in and the inside-out gimballing arrangements.The outside-in is, perhaps, the more conventional of the two gimballingarrangements. The gyros and accelerometers are mounted in a compactpackage and the gimbal rings required to give the necessary degrees offreedom are wrapped around this center. When utilizing this arrangement,all of the gimbal rings must be of sufficient dimension to clear theinstrument package when they are rotated. This factor results inplatforms of relatively large size.

In the inside-out gimballing arrangement, the gyros and accelerometershave traditionally been mounted in dumbbell fashion, connected by astiff post. Gimbals are 7 built up around the post to provide freedom ofmovement about the required area. The dumbbell arrangement ofinstruments is born within the next outer gimbal (usually the inner rollgimbal) such that it is free to rotate about one of the positional axes(usually the azimuth axis). The inside-out gimballing arrangementresults in a potentially more compact package since only the outergimbal need be of sufficient size to clear the instrument package.

When four-gimbal platforms are necessitated by the particular workingenvironment, the inside-out gimballing arrangement has the additionaladvantage of positioning the sensitive components such that access tothem may be gained easily without disassembling the entire gimballingstructure. This important feature allows interchange and repair ofcomponents with relative ease and with down periods of relatively shortduration.

As will be appreciated by those skilled in the art, one of the majorproblems in stabilized platform design is the effective incorporationwithin the system of torquers, resolvers, pick-offs, switches and thelike. The major problem which heretofore has plagued designers ofinside-out gimballing arrangements is the incorporation of these sensingand control elements into the gimbal joint between the dumbbell-shapedgimbal or component support platform and the succeeding outer gimbal.Because of balance considerations, the weights at the opposite ends ofthe dumbbell shaft must be approximately equal. It has been customary toconnect these weightsi.e. the

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component mounting platforms and the components thereon-by means of asolid shaft which extends through and is rotatably born by thesucceeding outer gimbal. This arrangement does not permit theutilization of conventional axially symmetrical slip rings, brushblocks, torquers, resolvers and the like. Therefore, complicated geartrains are necessary to transmit rotational position signals to and fromthe dumbbell-shaped gimbal. Gear trains of this type rapidly become verycomplicated. In addition to being extremely expensive to fabricate, anyslight discrepancy in the gear surfaces results in a cumulative errorwhich well may render the system unusable. Modern day space requirementsnecessitate gyroscopic platforms which are capable of functioningcontinually with a very slight error. It follows, therefore, that anycomponent such as a gear train which inherently introduces positionalerrors into the system must be avoided. Therefore, the tendency ofmanufacturers has been to accept the relatively large instrumentpackages and difficult access procedures inherent in the outside-ingimballing arrangements in order to reduce positional errors to withinacceptable limits.

It is an object of this invention to provide a gimballing arrangementfor utilization in three and four gimball platforms which capitalizes onthe inherent advantages of an inside-out gimballing arrangement and,yet, is not subject to the disadvantages which have been previouslyassociated therewith.

More particularly, it is an object of this invention to provide agimballing arrangement which provides a relatively small componentpackage.

It is an object of this'invention to provide a gimballing arrangementwherein access to the critical components may be gained withoutdisassembling the entire gimballing system.

It is an object of this invention to provide an insideout gimballingarrangement which does not require the utilization of complicated geartrains to transmit rotational position signals to and from the innermostgimbal, and thus to reduce both the expense and inherent cumulativeerror of the system.

These and other objects of this invention will be clearly understood byreference to the following specifications and accompanying figures inwhich:

FIG. 1 is a stick diagram of a representative 3 gyro four-gimbalplatform;

FIG. 2 is a fragmentary repspective, partially in crosssection, of afour-gimbal platform embodying the gimballing arrangement which is thesubject of this invention;

FIG. 3 is a perspective view of the inner roll-azimuth axes platformassembly;

FIG. 4 is a side-elevational view, partially in crosssection, of theinner roll gimbal; and

FIG. 5 is a cross-sectional view taken along line VV of FIG. 3.

Briefly, this invention comprises an inside-out gimballing arrangementwherein the component mounting platforms are each rotatably affixed to adistinct one of a pair of axially aligned sleeves projecting fromopposite sides of the succeeding outer gimbal. Brush blocks are affixedto the inner peripheries of the sleeves and a slip ring insertedthereinto. The slip ring has a mounting cap affixed to the adjacentplatform whereby it rotates with respect to its associated brush blockwhen that platform experiences rotation relative to the succeeding outergimbal. Means are provided whereby stationary components of resolvers,torquers, and the like may be affixed to the succeeding outer gimbalsymmetrical to the mounting sleeve. Similarly, the rotating componentsof these devices may be aflixed to the component bearing platformsymmetrical about the support sleeve.

The rotational positions of the two platforms are maintained byproviding a circular flange aflixed to each of the component supportingplatforms. The flanges converge into the space between the two platformsand have circular rack gears on their facing surfaces. A pair of spurgears having diameters substantially less than the diameter of the rackgears are carried by the succeeding outer gimbal frame in such a mannerthat they transmit the rotational thrust of one of the platformsdirectly to the other platform, thus insuring that the relative angularpositions of the two platforms with respect to the succeeding outergimbal will always be identical.

Referring now to the figures, a preferred embodiment of this inventionwill be described in detail. FIG. 1 is a stick diagram of a conventional3 gyro, four-gimbal platform. This diagram will be utilized as a meansof presenting a typical environment in which the subject matter of thepresent invention finds usage. This diagram is not intended toillustrate the details of the inventive gimballing arrangement, nor doesit do so. On the contrary, it is virtually impossible to accuratelydepict an inside-out gimballing arrangement in stick form. Therefore,the diagram is functional, rather than structural, in nature.

As will be seen by reference to FIG. 1, the frame has an outer rollgimbal 11 pivotably joined thereto. Proceeding inwardly, pitch gimbal 12is jointed to outer roll gimbal 11, inner roll gimbal 13 is pivotablyjointed to pitch gimbal 12, and azimuth gimbal 14 (also commonlyreferred to as the component mounting platform) is pivotably jointed toinner roll gimbal 13. Azimuth gimbal 14 carries three accelerometers 15and three gyros 16-. These components, as is well-known in the art, arepositioned such as to provide positional signals within the coordinatesystem defined by azimuth axis 17, pitch axis 18, outer roll axis 19 andinner roll axis 20.

As is also well-known, the gyroscopic components 16 each have levelingaxes with torquers and pickoffs mounted thereon. Thus, azimuth levelingaxis 21 has torquer 22 and pickoif 23 associated therewith, rollleveling axis 24 has torquer 25 and pickoff 26 associated therewith and,pitch leveling axis 27 has torquer 28 and pickoif 29 associatedtherewith.

As is similarly well-known, the gimbal joint between the outer rollgimbal and the pitch gimbal incorporates a torquer 30, a synchro 31, anda pitch segment switch 32. The gimbal joint between the azimuth gimbaland the inner roll gimbal incorporates a torquer 33, a synchro 34, andone or a plurality of resolvers 35. The gimbal joint between the innerroll gimbal and the pitch gimbal incorporates torquer 36 and synchro 37.Finally, the gimbal joint between roll gimbal 11 and frame 10incorporates torquer 38, synchro 39, and a roll segment switch 40.Merely by way of example, the pitch leveling axis may be limited torotational movement of a plus or minus five degrees, the azimuthleveling axis to plus or minus five degrees, the roll leveling axis toplus or minus five degrees, and the inner roll axis to a plus or minusten degrees. The remainder of the axes-Le. the outer roll, azimuth andpitchare, of course, free to rotate a full 360 degrees.

All of the functional interrelationships of the component shown in FIG.1 are well-known in the art. The problem, as pointed out previously, isone of packaging and structurally interrelating these components suchthat thedesired degree of accuracy may be obtained from a structurewhich is as small as possible and within which access may be gained tothe critical components with relative ease. Referring now to FIGS. 2through 5, the insideout gimballing arrangement which is the subject ofthis invention will be illustrated.

FIG. 2 shows a housing having mounting means 51 whereby it may beafiixed to the vehicle within which its components are to function. Thehousing 50 encloses an outer roll gimbal 52, a pitch gimbal 53, and aninner roll gimbal 54. The reference numeral 55 indicates generally thehousing-outer roll gimbal joint, the reference numeral 56 the outerroll-pitch gimbal joints, and the reference numeral 57 the pitch-innerroll gimbal joints. A plurality of balancing lugs 58 are positionedthroughout the system in a well-known manner such that the overallstructure may be balanced prior to insertion in the vehicle.

The inner roll-azimuth axis platform assembly 60 comprises a pair ofaxially aligned sleeves 61a and 61b which project from the circularplanar midsection 62 of inner roll gimbal 54. The reference letters aand b will be utilized hereinafter to indicate those correspondingcomponents on opposite sides of inner roll gimbal 54, however, thesereference letters may henceforth be omitted in the discussion of anycomponent part of the instant invention for the sake of brevity andclearness. As will become apparent, the platform structures on oppositesides of inner roll gimbal 54 are identical, the overall structuresdiffering only in the types of components and controls which areassociated therewith. The circular planar midsection '62 of inner rollgimbal 54 has a pair of circular upstanding flanges 63a and 63bextending from opposite sides thereof. Each of these flanges includes adetent 64a and 64b respectively. Planar midsection 62 is carried by apair of conventional mounting wheels 65 aflixed to opposite symmetricalextremities thereof.

The component support platforms 74a and 74b are circul-ar and each hasan inner depending circular flange 75 associated therewith (see FIG. 5).Flanges 75 have detents 76 and bearing retainer notches 77 for-medintegrally therewith. Spaced radially outwardly from inner dependingcircular flange 75 on component platform 74 is an outer dependingcircular flange 78. Flange 78 also has a detent 79 integrally associatedtherewith. A circular gear flange 80 is radially displaced from flanges75 and 78 and, conveniently, forms the outer boundary of componentsupport platforms 74. Circular gear flanges 80a and 8% have circulargear racks cut in their facing surfaces as will become apparenthereinafter.

The component support platforms 74 are rotatably mounted to supportsleeves 61 by means of inner and outer bearing assemblies 66 and 67.Each of these bearings has an inner race 68 and an outer race 69 and thetwo assemblies are spaced by means of an inner spacer 71 and an outerspacer 72. As will be seen by reference to FIG. 5, inner spacer 71 isassociated with inner bearing races 68 and outer spacer 72 is associatedwith outer bearing races 69. By varying the lengths of these spacers,minor imperfections in the width of the bearing races may becompensated. The bearing assemblies are positioned adjacent to the innerroll gimbal 54 by means of a bearing retainer notch 73 on sleeve 61 andbearing retainer notch 77 on component support platform 74. Circularbearing locks 82 and 95 are screwed into their respective threadedreceviers on sleeve 61 and cap 74. Bearing locks 82 and 95 function tocontrol and maintain the axial displacement of platform '74 with respectto inner roll gimbal 54. Shims 99a and 99b are used to set the axialposition of gears 80a and 8% so that minimum gear tooth clearance can bemaintained between gear teeth 80a and 80b, and the working faces of spurgears 91 and 92.

Mounted between circular planar midsection 62 of inner roll gimbal 54and platform 74 by means of detents 64, 76, and 79 are a series ofresolvers and torquers. For example, resolver rotor 83 is aflixed toplatform 74 while its adjacent stator 84 is aflixed to inner roll gimbal54. Similarly, a torquer winding 85 might be affixed to platform 74while its associated permanent magnetic field 86 is aflixed to innerroll gimbal 54. As is well-known in the art, the relative rotationbetween the associated compo nents of these devices is controlled by orcontrols particular functions within the platform and vehicle with whichit is associated. As a rule, in devices of the type shown, threeresolvers and only one torquer are utilized. Therefore, both of thecontrol component spaces in the a section of the assembly might containresolvers while only one of the control spaces in the b section containsa resolver, the other such space being reserved for a torquer.

A conventional slip ring 87 is positioned within brush block 88 by meansof a slip ring retainer cap 82 which is aifixed to platform 74. Thus,electrical signals may be transmitted from the 360 degree pivotablesupport platform 74 without necessitating the use of flexible leads. Itwill be appreciated by those skilled in the art that all of thecomponents shown in FIG. are circular or cylindrical in plan viewwhereby they may be mounted symmetrically about sleeves 61.

It is, of course, necessary that the two support platforms 74a and 7 4bbe slaved in some manner to insure that their relative radialdisplacements with respect to. inner roll gimbal 54 always remain thesame. As pointed out previously, past devices have utilized a solidshaft extending through inner roll gimbal 54 and connecting the facingsupport platforms 74 for this purpose. The presence of this shaft,however, made it impossible to utilize conventional Slip ring and brushblock connections and thus necessitated the use of complicated geartrains to transmit the rotational information to and from the componentsmounted on platforms 74. That is to say, the use of the solid shaftforeclosed any possibility of axially symmetrically mounting the controland signal components atthe gimbal joint. It will be obvious from anexamination of FIG. 5 that-the present invention obviates this problem.

The relative rotational displacements of platforms 74a and 74b withrespect to inner roll gimbal 54 is maintained constant by means of twospur gear assemblies 90 which are carried by opposite sides of innerroll gimbal 54. These spur gears engage the circular gear rack faces offlanges 80 on platforms 74 and transmit any rotational displacement ofone such platform to the other. While it would be possible to utilizeonly one spur gear assembly 90, it has been found that the tendency forthese gears to jam or be pulled free from their intermeshingrelationships with flanges 80 is alleviated by utilizing two suchassemblies displaced 180 degrees from one another. Conveniently, spurgear assemblies 90 may be carried at points on circular planarmidsection 62 of inner roll gimbal 54 which are displaced 90 degreesfrom the mounting Wheels 65. Thus, when one of the platforms 74experiences any slight degree of rotation, that same degree of rotationis positively transmitted to its mating platform, assuring that the twowill maintain an identical angular displacement with respect to innerroll gimbal 54.

It is important that the diameter of spur gears 91 and 92 be keptrelatively small in relation to the diameter of the circular gear racks80. If, for example, a ratio of 5 to l is utilized, any slippagetendency within the spur gear assemblies 90 will be reduced by a factorof 5 prior to the time that this slippage has been transmitted to the individual component mounting platforms 74.

The bearing construction shown in FIG. 5 whereby the component mountingplatforms may rotate about sleeves 61 has a number of distinctadvantages; For example, the sizes of these spacers 71 and 72 may beindividually determined so as to compensate for varying width bearingraces. The thickness of shims 99 may be varied so as to insure that theaxial displacement of circular gear racks 80a and 80b will preciselyaccommodate spur gears 91 and 92, thus preventing any slippage in themechanical servoing connection. Any tendency towards overall axialbearing play may be eliminated by controlling the size of spacers 71 and72 and the individual tightness of bearing caps 82 and 95.

Once the platforms 74a and 74b have been mounted, the gyroscopicinstrument packages 93a and 93b may be atfixed thereto in anyconventional manner. In addition to gyroscopes and accelerometers,instrument packages 93a and 93b will undoubtedly include electronicmodules and other types of conventional components. In the device shown,for example, two of the gyros might be placed on platform 74a while onegyro and the three accelerometers are positioned on platform 74b.

From an examination of FIG. 2, it will be apparent that the presentconstruction enables components to be utilized at the inner roll-azimuthaxis joint which are highly similar, if not identical, to those utilizedat the other gimbal joints within the system. What this invention hasaccomplished effectively, is to allow the utilization of twoconventional gimbal joints such as indicated at 57 in back to backservoed relationship whereby the gyroscopic components may be mounted ondiverging, instead of facing, sides thereof. The sleeves 61a and 61ballow usage of conventional slip rings and brush blocks at the innerroll gimbal-azimuth axis joint. Thus, platforms 74a and 74b and thecomponents mounted thereon may rotate 360 degrees about the azimuth axiswithout requiring the utilization of complicated gear trains to controland power them. The construction shown in this invention retains theadvantages of utilizing integral components on the axes of the gimbaljoints without sacrificing the size reduction and easy access to partsinherently associated with inside-out gimbal structures.

In operation, as the vehicle experiences a maneuver about the azimuthaxis, platforms 74a and 74b rotate about their respective mountingsleeves 61a and 61b to maintain the position dictated by the azimuthgyro. The spur-gear assemblies 90, in conjunction with the circular gearracks 80, insure that the two facing platforms 74a and 74b will not tendto experience a radial displacement relative to one another. Thisconstruction is desirable even when separate torquers are utilized foreach of the gyro platforms and absolutely essential when, as usual, onlyone torquer is utilized to control the position of both of theplatforms.

Signals are transmitted to and from the instrument packages by means ofslip rings 87 and brush blocks 88. These signals, as is well-known inthe art, are transmitted to various components within the system suchthat positioned signals may be derived at the outputs thereof.

While a preferred embodiment of this invention has been described indetail, it will be apparent to those skilled in the art that a number ofmodifications thereof may be executed without departing from the spiritand scope of this disclosure. Such modifications are to be deemed asincluded in the following claims unless these claims, by their language,expressly state otherwise.

I claim:

1. An inside-out gimballing arrangement comprising:

a gimbal having a pair of axially aligned sleeves extending fromopposite sides thereof; and

a component mounting platform rotatably connected to the outercircumference of each of said sleeves such that said gimbal lies betweensaid platforms, said platforms being rotationally slaved together bymeans of circular gear racks affixed to the surfaces thereof, said gearracks having their toothed surfaces positioned in parallel planes, andgear means coupling said gear racks.

2. The combination as set forth in claim 1 which further comprises slipring and brush block components positioned within each of said sleeves,one of said components being aflixed to said gimbal and the other beingaffixed to the adjacent platform.

3. The combination as set forth in claim 1 wherein said gear meanscomprises two sets of spur gears rotatably mounted on said gimbal, eachof said sets consisting of two spur gears which intermesh with eachother and with the circular gear racks on said platforms, said setsbeing positioned at diametrically opposite locations on said gear racks.

4. The combination as set forth in claim 3 wherein the diameter of saidspur gears is substantially less than the diameter of said circular gearracks.

5. A gimballing system comprising:

a gimbal having a pair of aligned supports extending from opposite sidesthereof;

a component mounting platform rotatably connected to each of saidsupports such that said gimbal lies between said platforms;

circular flanges affixed to the surfaces of each of said platforms, saidfianges each having circular gear racks thereon; and I gear meanscoupling said gear rack surfaces whereby said platforms are rotationallyslaved.

6. The combination as set forth in claim 5 wherein said aligned supportsare hollow, said platforms being mounted to the outer peripheriesthereof.

7. The combination as set forth in claim 6 wherein said supports haveslip ring and brush block components inserted in the hollow sectionsthereof, one of said components being affixed to said gimbal and theother being affixed to the adjacent platform.

8. The invention as recited in claim 7, wherein each of said pairofaligned supports is fixedly connected to said gimbal.

9. In an inertial platform having an outer roll gimbal, a pitch gimbaland an inner roll gimbal, the combination comprising:

a pairof axially aligned sleeves extending from opposite sides of saidinner roll gimbal;

a component mounting platform rotatably connected to the outercircumference of each of said sleeves, said platforms serving as azimuthgimbals having gyroscopic accelerometer components mounted thereon; and

means coupling said platforms whereby said platforms are rotatablyslaved together.

10. The combination as set forth in claim 9 which further comprises slipring and brush block components positioned within each of said sleeves,one of said components being affixed to said inner roll gimbal and theother being aflixed to the adjacent platform.

. 11. In an inertial platform having a gimbal, the combinationincluding: a

a pair of oppositely-directed supports rigidly connected to said gimbal;and

a pair of component mounting platforms, each connected to one of saidsupports and rotatable with respect thereto, said platforms serving asazimuth gimbals having gyroscopic and accelerometer components mountedthereon wherein said component mounting platforms are slaved togetherpreventing relative movement therebetween.

References Cited UNITED STATES PATENTS 12,949,785 8/1960 Singleton et al74 5.34

ROBERT F. STAHL, Primary Examiner

